Motor-operated compressor

ABSTRACT

A motor-operated compressor includes a casing having a motor chamber that accommodates a driving motor. The compressor also includes a frame. A first scroll having a first spiral wrap is connected to one side of the frame. A second scroll is provided between the frame and the first scroll. The second scroll has a second spiral wrap that engages with the first spiral warp to form compression chambers between the first and second spiral wraps. The compressor also includes a rotation shaft connected at one end to the driving motor and at an opposite end to the second scroll. The compressor includes a back pressure space defined by a balance weight axially separated from a rear surface of the second scroll. A back pressure passage fluidly connects the compression chambers with the back pressure space.

CROSS-REFERENCE TO RELATED APPLICATION

Pursuant to 35 U.S.C. § 119(a), this application claims the benefit of earlier filing date and right of priority to Korean Application No. 10-2018-0106673, filed on Sep. 6, 2018, the contents of which is incorporated by reference herein in its entirety.

BACKGROUND OF THE DISCLOSURE 1. Field of the Disclosure

The present invention relates to a scroll type motor-operated compressor.

2. Background Art

Generally, compressors for compressing a refrigerant in automotive air conditioning systems have been developed in various forms. Recently, motor-operated compressors driven by electric power using motors have been actively developed according to the tendency of electricization of electric parts of vehicles.

A motor-operated compressor mainly employs a scroll compression method suitable for a high compression ratio operation. In the scroll type motor-operated compressor (hereinafter, abbreviated as ‘motor-operated compressor’), a motor unit configured as a rotary motor is installed in a hermetic casing, and a compression unit configured by a fixed scroll and an orbiting scroll is disposed at one side of the motor unit. The motor unit and the compression unit are connected to each other by a rotation shaft so that a rotational force of the motor unit is transferred to the compression unit.

As disclosed in Patent Document [Japanese Laid-Open Patent Application No. 2014-125957], the related art motor-operated compressor is provided with an inner motor chamber, a suction space defining a motor chamber and accommodating sucked refrigerant and oil therein, a discharge space accommodating refrigerant and oil discharged from a compression chamber and defining a sort of oil separation space, and a back pressure space accommodating mist-state oil (hereinafter, referred to as ‘gas oil’) separated from the refrigerant in the discharge space, so that pressure of the gas oil pushes an orbiting scroll toward a fixed scroll. The suction space is formed in a main housing forming a casing, the discharge space is formed in a rear housing constituting the casing together with the main housing, and the back pressure space is formed in a main frame which is coupled to the main housing to support the orbiting scroll in an axial direction.

In the related art motor-operated compressor, the fixed scroll (and/or the main frame) is provided with a back pressure passage so that gas oil is supplied to the back pressure space from the discharge space. In this case, a pressure reducing device is installed in the back pressure passage to control pressure of the back pressure space by reducing the pressure of the gas oil supplied to the back pressure space.

However, in the related art motor-operated compressor, as described above, the back pressure of the back pressure space is affected by pressure of the discharge space rather than pressure of the compression chamber as the back pressure space communicates with the discharge space via the back pressure passage. Accordingly, the back pressure is usually constantly maintained even if there is a pressure change in the compression chamber during operation. As a result, when the back pressure is higher than required back pressure, friction loss increases due to excessive adhesion between the two scrolls. On the other hand, when the back pressure is lower than the required back pressure, compression loss may occur due to excessive spacing between the two scrolls.

In the related art motor-operated compressor, the back pressure space is formed in a back pressure space portion in which a balance weight is accommodated, which increases the volume of the back pressure space. As a result, it is hard to quickly secure the back pressure at the beginning of operation.

Also, in the related art motor-operated compressor, a main bearing is provided in the back pressure space. However, due to this structure, an excessive load caused by the pressure of the back pressure space is applied to the main bearing, thereby decreasing lifespan of the main bearing.

In addition, in the related art motor-operated compressor, a sealing member for forming the back pressure space is inserted into the orbiting scroll or the main frame. However, it may cause difficulty in securing required sealing force if the pressure in the back pressure space rises excessively. In particular, even in the case of a high-pressure refrigerant such as a CO2 refrigerant in which back pressure rises up to 60 to 70 bar, behavior of the orbiting scroll may be made unstable as the back pressure space is not effectively sealed.

SUMMARY OF THE DISCLOSURE

One aspect of the present invention is to provide a motor-operated compressor, capable of securing and maintaining required back pressure of a back pressure space.

Another aspect of the present invention is to provide a motor-operated compressor in which back pressure of a back pressure space is interlocked with pressure of a compression chamber.

Still another aspect of the present invention is to provide a motor-operated compressor, capable of quickly forming required back pressure inside a back pressure space.

Still another aspect of the present invention is to provide a motor-operated compressor, capable of smoothly supporting an orbiting scroll while decreasing a volume of a back pressure space.

Still another aspect of the present invention is to provide a motor-operated compressor, capable of reducing load applied to a main bearing accommodated in a back pressure space so as to extend lifespan of the main bearing.

Still another aspect of the present invention is to provide a motor-operated compressor, capable of reducing manufacturing costs by simplifying a structure of a pressure reducing device and reducing the number of components of the pressure reducing device.

In order to achieve the aspects of the present invention, there is provided a motor-operated compressor, including a compression chamber formed between a first scroll and a second scroll, a back pressure space provided to support the second scroll toward the first scroll, and a back pressure hole provided at the second scroll for guiding some of a refrigerant compressed in the compression chamber to the back pressure space, wherein the back pressure space is formed between a balance weight coupled to a rotation shaft together with the second scroll weight and the second scroll.

Here, the second scroll may be provided with a sealing groove formed therein so that a sealing member for forming the back pressure space is slidably inserted, and the sealing groove may be provided with a pressure hole communicating with the compression chamber to guide some of a refrigerant compressed in the compression chamber to an opposite side of a sealing surface of the sealing member.

The pressure hole may communicate with the back pressure hole.

Further, in order to achieve those aspects of the present invention, there is provided a motor-operated compressor, including a casing having a motor chamber, a frame provided at one side of the motor chamber, a driving motor provided at one side of the frame and accommodated in the motor chamber, a first scroll supported on another side of the frame and having a spiral wrap, a second scroll having a spiral wrap engaged with the wrap of the first scroll, and forming compression chambers between the wraps while performing an orbiting motion by receiving a rotational force of the driving motor, a rotation shaft having one end connected to a rotor of the driving motor and another end eccentrically coupled to the second scroll to transfer the rotational force of the driving motor to the second scroll, a balance weight provided with one surface facing a rear surface of the second scroll and coupled to the rotation shaft, a sealing member provided between the rear surface of the second scroll and the one surface of the balance weight to form a back pressure space between the rear surface of the second scroll and the one surface of the balance weight, and a back pressure passage formed through the second scroll so that the compression chamber and the back pressure space communicate with each other.

Here, the second scroll may be provided with a sealing groove formed in an annular shape so that the sealing member is slidably inserted therein in an axial direction. The second scroll may be provided with a pressure passage formed therethrough so that the sealing groove and the compression chamber communicate with each other.

The pressure passage may be formed to be smaller than or equal to a thickness of the wrap.

The pressure passage may communicate with a discharge chamber to which a discharge port is belonged, or with a compression chamber immediately before the discharge chamber.

The back pressure space may have a radial area larger than or equal to a radial area of the compression chamber communicating with the pressure passage.

The back pressure passage may communicate with the pressure passage.

The back pressure passage may have an inner diameter smaller than or equal to an inner diameter of the pressure passage.

The back pressure passage and the pressure passage may be formed to be independent from each other.

The back pressure passage and the pressure passage may be formed to communicate with the same compression chamber.

Here, the second scroll may be provided with a back pressure protrusion portion annularly protruding toward the balance weight. The back pressure protrusion portion may be provided with a sealing groove in which the sealing member is slidably inserted in the axial direction. The pressure passage may be formed through the second scroll at an inner side than an inner circumferential surface of the back pressure protrusion portion.

The second scroll may be provided with a back pressure space groove recessed by a predetermined depth from a surface facing the balance weight, a sealing groove may be formed at an outside of the back pressure space groove so that the sealing member is slidably inserted therein in the axial direction, and the back pressure passage may be formed to penetrate through an inside of the back pressure space groove.

The balance weight may include an eccentric pin portion fixed to the rotation shaft and coupled to the second scroll, an eccentric mass portion extending from the eccentric pin portion and having a center of gravity eccentrically positioned from a center of the rotation shaft, and a back pressure surface portion extending radially from the eccentric pin portion at an opposite side of the eccentric pin portion, to form a back pressure space portion together with the eccentric mass portion.

Here, the frame may be provided with an accommodating space portion for accommodating the balance weight, and the accommodating space portion may communicate with the motor chamber.

The accommodating space portion may be provided with a bearing supporting portion formed on one side thereof in a stepped manner, and the bearing supporting portion may be provided with a ball bearing for supporting the rotation shaft.

Here, the second scroll may be provided with a boss groove to which the rotation shaft is coupled, and a bush bearing may be provided between an inner circumferential surface of the boss groove and an outer circumferential surface of the rotation shaft.

Here, the casing may be provided with a discharge space accommodating a refrigerant and oil discharged from the compression chamber, the discharge space may be provided with an oil recollecting passage to guide a refrigerant and oil in the discharge space to a suction side of the compression chamber, and the oil recollecting passage may be provided with a pressure reducing member.

In a motor-operated compressor according to the present invention, since pressure of a back pressure space interacts with pressure of a compression chamber, the pressure of the back pressure space can vary according to the change in the pressure of the compression chamber, thereby maintaining required back pressure. This may result in suppressing friction loss that may occur when the pressure of the back pressure space is higher than the required back pressure, and suppressing compression loss that may occur when the back pressure is lower than the required back pressure.

In addition, in a motor-operated compressor according to the present invention, since a back pressure space is formed between a second scroll and a balance weight, a volume of the back pressure space decreases, thereby forming required back pressure quickly and enhancing compressor efficiency. Also, a back pressure hole communicates with a compression chamber that forms discharge pressure or a compression chamber immediately before a discharge chamber, so that the required back pressure can be secured more quickly even if the volume of the back pressure space is decreased. Furthermore, a radial area of the back pressure space is wider than that of the compression chamber communicating with the back pressure space, resulting in stably supporting an orbiting scroll.

Furthermore, in a motor-operated compressor according to the present invention, since a main bearing that supports a rotation shaft is installed outside of a back pressure space, load generated by high pressure in the back pressure space is not directly applied to the main bearing, thereby extending lifespan of the main bearing.

In addition, in a motor-operated compressor according to the present invention, sealing force of a sealing member forming a back pressure space can be improved by supporting the sealing member axially by a pressure hole communicating with a compression chamber. Accordingly, the back pressure space can be effectively sealed even when a high-pressure refrigerant such as a CO2 refrigerant is used, which may result in securing required back pressure smoothly.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 2 are an exploded perspective view and an assembled sectional view of a motor-operated compressor according to the present invention.

FIG. 3 is an exploded perspective view of an orbiting scroll and a balance weight forming a back pressure space in the motor-operated compressor according to the present invention.

FIG. 4 is an assembled sectional view of a compression unit including the orbiting scroll and the balance weight of FIG. 3.

FIG. 5 is an enlarged sectional view of a part “A” of FIG. 4.

FIGS. 6A and 6B are enlarged planar views illustrating the vicinity of a discharge chamber to explain embodiments relating to positions of a pressure hole and a back pressure hole.

FIG. 7 is a planar view illustrating a balance weight according to an exemplary embodiment of the present invention.

FIGS. 8A to 9B are sectional views illustrating a position of an orbiting scroll depending on a pressure difference between a compression chamber and a back pressure space in the motor-operated compressor according to the present invention.

FIG. 10 is a sectional view illustrating another embodiment of a back pressure space in the motor-operated compressor according to the present invention.

DETAILED DESCRIPTION

Description will now be given in detail of a motor-operated compressor according to exemplary embodiments disclosed herein, with reference to the accompanying drawings.

A motor-operated compressor according to the present invention is a part of a refrigeration cycle apparatus which sucks and compresses a refrigerant, namely, a scroll compressor, in which two scrolls are engaged with each other to compress a refrigerant. This embodiment of the present invention illustrates a high-temperature and high-pressure motor-operated scroll compressor that uses a carbon dioxide (CO2) refrigerant having discharge pressure of 100 bar, more precisely, of about 130 bar and a discharge temperature of about 170° C. FIGS. 1 and 2 are an exploded perspective view and an assembled sectional view of a motor-operated compressor according to the present invention.

Referring to FIGS. 1 and 2, a motor-operated compressor according to this embodiment may include a casing 101, a main frame 102, a driving unit 103, and a compression unit 104. An inverter unit 200 for controlling an operation of the compressor may be installed outside a front cover 112 to be described later. Accordingly, the inverter unit 200 may be located at the opposite side of the compression unit 104 with respect to the driving unit 103. Hereinafter, for the sake of explanation, a side where the inverter unit is located is designated as a front side and an opposite side where the compression unit is located is designated as a rear side.

The casing 101 may include a main housing 111, a front cover 112, and a rear cover 113.

The main housing 111 has a cylindrical shape with opened front and rear ends. The front cover 112 may be coupled to the front end and the rear cover 113 may be coupled to the rear end. A suction space S1 constituting a motor chamber may be formed in the main housing 111, and a discharge space S2 may be formed by the rear cover 113 together with a first scroll 140, which is to be explained later, inside the rear cover 113.

The suction space S1 is provided therein with the driving unit 103, a frame and the compression unit 104, and the discharge space S2 may be provided therein with an oil separator 116 for separating oil from a refrigerant introduced thereinto.

Also, an inlet port 111 a communicating with the suction space S1 is formed at a side wall of the main housing 111, and an exhaust port 113 a communicating with the discharge space S2 is formed at a side wall of the rear cover 113. The oil separator 116 may be installed in the exhaust port 113 a.

In addition, a first oil recovery hole 113 b for recovering oil separated by the oil separator 116 is formed in a lower part of the rear cover 113. A second oil recovery hole 142 a for guiding gas oil recovered through the first oil recovery hole 113 b to a suction chamber V1 may be formed in the first scroll 140. The first oil recovery hole 113 b or the second oil recovery hole 142 a may be provided with an orifice 117 for decompressing the gas oil guided to the suction chamber V1. Accordingly, since the discharge space communicates with the suction chamber V1 through the first oil recovery hole 113 b and the second oil recovery hole 142 a, a series of processes of recovering the oil separated by the oil separator 116 to the suction chamber V1 in a mixed state with gas may occur. This will be described again later.

Meanwhile, the main frame 102 may be formed with a body portion 121 in an annular disc shape, and an edge of the body portion 121 may be connected in a supported manner between a front surface of a scroll side wall 142 of the first scroll 140 and an inner stepped surface 111 b of the main housing 111. A first sealing member 171 is provided on a bearing surface 150 a of a second scroll 150 in contact with a bearing surface 121 a of the body portion 121 so as to seal a thrust bearing surface between the main frame 102 and the second scroll 150.

Also, a balance weight accommodating space portion (hereinafter referred to as ‘accommodating space portion’) 122 for accommodating a balance weight 136 to be described later may be formed at a central part of the main frame 102. The balance weight 136 may be rotatably accommodated in the accommodating space portion 122 and connected to a rotation shaft 135 for compensating imbalance caused by an eccentric orbiting motion of the second scroll 150. The balance weight 136 forms a back pressure space together with the second scroll 140 to be described later, which will be explained later together with a back pressure hole.

Also, a shaft receiving portion 123 is formed at a central part of the accommodating space portion 122 in a manner of protruding toward a front side, and a shaft hole 124 in which the rotation shaft 135 is rotatably inserted is formed through a central part of the shaft receiving portion 123. The main bearing 161 described above is fixedly coupled to an inner circumferential surface of the shaft receiving portion 123, and an inner circumferential surface of the shaft hole 124 is spaced apart from an outer circumferential surface of the rotation shaft 135. Accordingly, a rear side of the accommodating space portion 122 is sealed by the first sealing member 171, but a front side of it is opened to communicate with the suction space S1.

Meanwhile, the driving unit 103 includes a stator 131 and a rotor 132, and generates a rotational force to drive the rotation shaft 135. In the embodiment of the present invention, the stator 131 may be fixed to an inner circumferential surface of the main housing 111 and formed in an annular shape to create a cylindrical space therein. The rotor 132 may be disposed in the inner space of the stator 131 with being spaced apart from the stator 131. The rotor 132 may be formed substantially in a cylindrical shape, and the rotation shaft 135 may be coupled to a central part of the rotor 132. When power is supplied to the driving unit 103, the rotor 132 and the rotation shaft 135 can be rotated together by interaction between the stator 131 and the rotor 132.

The rotation shaft 135 may be accommodated in the main housing 111 and rotably supported on the main frame 102. A rear side of the rotation shaft 135 may be supported radially by a main bearing 161 mounted on the main frame 102. The main bearing 161 may be configured as a deep groove ball bearing having an inner ring connected to the rotation shaft 135 and an outer ring connected to the main frame 102, and press-fitted into the main frame 102.

In addition, a front end portion of the rotation shaft 135 may be radially supported by a sub bearing 162 provided on the front cover 112. The sub bearing 162 may be mounted on a shaft supporting protrusion portion 114 formed on an inner surface of the front cover 112. Accordingly, a part of an outer circumferential surface of the rotation shaft 135 may be connected to the rotor 132 so as to receive the rotational force generated by the driving unit 103.

Meanwhile, the compression unit 104 may include the first scroll 140, which is a fixed scroll, and the second scroll 150, which is an orbiting scroll. The second scroll 150 is eccentrically coupled to the rotation shaft 135 connected to the rotor 132 of the driving unit 103 and performs an orbiting motion with respect to the first scroll 140. During the orbiting motion, the second scroll 150 forms, together with a first scroll, a pair of compression chambers V each having a suction chamber V1, an intermediate pressure chamber V2, and a discharge chamber V3.

The first scroll 140 is provided with a fixed scroll disk portion 141 in a circular plate or disk shape, and a scroll side wall portion 142 protruding toward the main frame 102 may be formed on one side surface of the fixed scroll disk portion 141. The scroll side wall portion 142 may be provided with the second oil recovery hole 142 a, which is to be described later, formed therethrough in an axial direction.

A fixed wrap 143 may be formed by protruding from a central part of the fixed scroll disk portion 141 and engaged with an orbiting wrap 152 to be explained later to form a pair of compression chambers V. A suction port (not shown) which communicates with a suction space S1 of a casing 101 may be formed at an edge of the fixed scroll disk portion 141. And a discharge port 144 through which a final compression chamber communicates with the discharge space S2 may be formed at a central part of the fixed scroll disk portion 141.

The second scroll 150 is provided with an orbiting scroll disk portion 151 in a disk shape, and an orbiting wrap 152 protruding toward the fixed scroll disk portion 141 and engaged with the fixed wrap 143 is formed on a first side surface 151 a of the orbiting scroll disk portion 151. And a boss groove 153 is formed in a second side surface of the orbiting scroll disk portion 151 so that an eccentric bearing 163 for supporting the rotation shaft 135 is fixedly inserted therein. Accordingly, the second scroll 150 and the rotation shaft 135 can be coupled to each other with interposing the eccentric bearing 163 and the balance weight 136 therebetween so that a rotational force can be transferred from the rotation shaft 135 to the second scroll 150.

In the drawings, an unexplained reference numeral 180 denotes a pin-and-ring type rotation preventing member.

The motor-operated compressor according to this embodiment of the present invention operates as follows.

That is, when power is applied to the driving unit 103, the rotation shaft 135 transfers a rotational force to the second scroll 150 while rotating together with the rotor 132. Then, the second scroll 150 eccentrically connected to the rotation shaft 135 performs an orbiting motion by an eccentric distance due to the rotation preventing member 180, and the compression chamber V is reduced in volume while continuously moving toward a radial center of the rotation shaft 135.

Therefore, a refrigerant flows into the suction space S1 constituting the motor chamber through the inlet port 111 a and is then introduced into the compression chamber V. At this time, the refrigerant can cool the stator 131 and the rotor 132 while passing through the driving unit 103.

Then, the refrigerant sucked into the compression chamber V is compressed while flowing to a central part along a movement path of the compression chamber V, and is discharged into the discharge space S2 formed between the first scroll 140 and the rear cover 113 through the discharge port 144.

The refrigerant discharged into the discharge space S2 is separated from oil in the discharge space S2, or is separated from oil while passing through the oil separator 116. The refrigerant is then discharged to a refrigeration cycle through the exhaust port 113 a. On the other hand, the separated oil remains in the discharge space S2 in a mist-state (i.e. gas oil mixed with a small amount of refrigerant), and this gas oil is recovered to the suction chamber V1 through the first and the second oil recovery holes. The recovered refrigerant is sucked into the intermediate pressure chamber V2 again together with an introduced refrigerant and compressed in the intermediate pressure chamber V2. Such compressed refrigerant is then discharged through the discharge chamber V3. Such series of processes are repeated.

Meanwhile, pressure of the back pressure space, that is, back pressure needs to be maintained properly so that the behavior of the second scroll, which is the orbiting scroll, can be maintained stably. If the back pressure is low, a supporting force for the second scroll is weakened, which reduces adhesion to the first scroll as the fixed scroll. As a result, leakage from the compression chamber may occur and compression loss may be increased. On the other hand, if the back pressure is too high, the second scroll may perform an orbiting motion while being excessively engaged with the first scroll, which may increase friction loss.

In particular, when a CO2 refrigerant is used, pressure of the back pressure space is approximately 60 to 70 bar, which is higher than that when other refrigerants (134 a, 410 a, etc.) are applied. However, the back pressure space may not be formed properly due to uneven sealing force of the sealing member that seals the back pressure space. Also load applied to the main bearing accommodated in the back pressure space increases, which may shorten lifespan of the main bearing.

Therefore, in the present invention, friction or compression loss can be suppressed by interacting pressure of the back pressure space with pressure of the compression chamber, sealing force for the back pressure space using the sealing member forming the back pressure space can be increased by supporting the sealing member using the pressure of the compression chamber, and the lifespan of the main bearing can extend by separating a main bearing installation space from the back pressure space.

FIG. 3 is an exploded perspective view of the orbiting scroll and the balance weight forming the back pressure space in the motor-operated compressor according to the present invention. FIG. 4 is an assembled sectional view of the compression unit including the orbiting scroll and the balance weight of FIG. 3. FIG. 5 is an enlarged sectional view of the part “A” of FIG. 4. FIGS. 6A and 6B are enlarged planar views illustrating the vicinity of the discharge chamber to explain embodiments relating to positions of a pressure hole and a back pressure hole.

Referring to these drawings, in the motor-operated compressor according to the embodiment of the present invention, a back pressure hole 158 may be formed in the orbiting scroll disk portion 151 of the second scroll 150, which is the orbiting scroll, and a second sealing member 172 for forming the back pressure space S3 may be provided outer than the back pressure hole 158. Accordingly, a refrigerant compressed in the compression chamber V and a part of oil are introduced into the back pressure space S3 through the back pressure hole 158, forming back pressure.

For example, as shown in FIGS. 3 and 4, a back pressure protrusion portion 155 axially protrudes in an annular shape from a second side surface 151 b of the orbiting scroll disk portion 151, that is, a side surface facing the balance weight, at an outside of the boss groove 153 in a radial direction. A sealing groove 156 with a predetermined width and depth is formed in an annular shape on a front end surface of the back pressure protrusion portion 155, that is, a surface facing a back pressure surface portion 136 c of the balance weight 136 to be described later. The sealing groove 156 has a width wide enough that the second sealing member 172 to be described later can slide in an axial direction, and may have a depth greater than or equal to an axial height of the second sealing member 172.

Accordingly, the second sealing member 172 formed in an annular shape is inserted into the sealing groove 156 to move in an axial direction according to a pressure difference between the compression chamber V and the back pressure space S3. The second sealing member 172 separate an inner space of the back pressure protrusion portion 155, more precisely, an inner space of the second sealing member 172 from an outer space, thereby forming the back pressure space S3 communicating with the back pressure hole 158.

In addition, a pressure hole 157 forming a pressure passage may be formed in the sealing groove 156. The pressure hole 157 communicates an inside of the sealing groove 156 with the compression chamber V to form a passage in which the second sealing member 172 is pressurized toward the balance weight 136 by pressure of the compression chamber V.

As shown FIGS. 4 and 5, the pressure hole 157 may be formed in a penetrating manner from an axial side surface facing the first scroll 140, among three side surfaces forming the sealing groove 156, to the second surface 151 b of the orbiting scroll disk portion 151 forming the compression chamber V.

Also, the pressure hole 157 may be formed in a linear, inclined or stepped shape. It may be formed appropriately depending on a position of a first pressurizing end 157 a exposed to a first side surface 151 a of the orbiting scroll disk portion 151 to form an inlet of the pressure hole 157 and a position of a second exit end 157 b exposed to an inside of the sealing groove 156 to form an outlet of the pressure hole 157.

In addition, the first pressurizing end 157 a of the pressure hole 157 may communicate with the intermediate pressure chamber V2 interposed between the suction chamber V1 and the discharge chamber V3 so as to use intermediate pressure. However, to allow the use of discharge pressure, the first pressurizing end 157 a may alternatively be formed to communicate with the discharge chamber V3 or the intermediate pressure chamber V2 immediately before the discharge chamber. This exemplary embodiment of the present invention mainly illustrates the case where the first pressurizing end 157 a of the pressure hole 157 communicates with the discharge chamber V3 as the area of the back pressure space S3 to be described later decreases.

An inner diameter D1 of the pressure hole 157 may substantially be a gap between adjacent orbiting wraps 152. However, if the inner diameter D1 of the pressure hole 157 is larger than a sectional area A of the orbiting wrap 152, the compression chambers V located on both sides of the orbiting wrap 152 may communicate with each other, which may cause friction loss. Therefore, it is preferable that the inner diameter D1 of the pressure hole 157 is smaller than or equal to the sectional area A of the orbiting wrap. The inner diameter D1 of the pressure hole 157 may also be smaller than a width t of the sealing groove 156.

Meanwhile, the back pressure hole 158 may be formed in the orbiting scroll disk portion 151. The back pressure hole 158 serves as a back pressure passage for communicating the compression chamber V and the back pressure space S3 with each other, and may be formed on one side of the pressure hole 157.

The back pressure hole 158 may be formed to communicate with the pressure hole 157 or may be formed independently from the pressure hole 157.

For example, as shown in FIG. 6A, the back pressure hole 158 may be branched from a middle portion of the pressure hole 157 in a communicating manner. In this case, pressure in the compression chamber V for pressurizing the second sealing member 172 becomes equal to pressure in the compression chamber V for forming back pressure, which may be preferable in that behavior of the second sealing member 172 can become stable and refrigerant leakage between the compression chambers V can be inhibited.

As shown in FIGS. 4 and 5, a first back pressure end 158 a forming an inlet of the back pressure hole 158 may be branched from a middle portion of the pressure hole 157 in a communicating manner, and a second back pressure end 158 b forming an outlet of the back pressure hole 158 may be penetratingly formed between the back pressure protrusion portion 155 and the boss groove 153. The back pressure hole 158 may be formed in a stepped manner as shown in the drawings, but it is illustrated for the sake of explanation. The back pressure hole 158 may alternatively be formed inclined in consideration of processability.

Here, an eccentric bearing 163 configured as a bush bearing, unlike the related art eccentric bearing, may be provided inside the boss grove 153. This is because employment of the bush bearing having a relatively small occupied area is advantageous for ensuring a required space to form the back pressure space S3 as the back pressure protrusion portion 155 and the second back pressure end 158 b of the back pressure hole 158 are formed on the second surface 151 b of the orbiting scroll disk portion 151 with a spacing therebetween in a radial direction

Also, an inner diameter D2 of the back pressure hole 158 may be formed to be the same as or different from the inner diameter D1 of the pressure hole 157. However, when the inner diameter D2 of the back pressure hole 158 is different from the inner diameter D1 of the pressure hole 157, the inner diameter D2 of the back pressure hole 158 may preferably be formed to be smaller than the inner diameter D1 of the pressure hole 157. Accordingly, a refrigerant and oil flowing to the back pressure hole 158 through the pressure hole 157 are decompressed to a pressure lower than a pressure for pressing the second sealing member 172 to form back pressure. Thus, the sealing member 172 can be pressed by force generated due to high pressure, resulting in increasing sealing force of the second sealing member 172.

Since an inlet of the back pressure hole 158 communicates with the discharge chamber V3 through the pressure hole 157, required back pressure may not be secured if an area of the discharge chamber V3 is equal to an area of the back pressure space S3. Therefore, an inner diameter of the back pressure protrusion portion 155 forming the back pressure space S3 or an inner diameter of the second sealing member 172 is preferably formed larger than an inner diameter of the discharge chamber V3 so that the area of the back pressure space S3 can be formed larger than the area of the discharge chamber V3.

Meanwhile, as described above, the back pressure hole 158 may be formed independently from the pressure hole 157. For instance, as shown in FIG. 6B, when the back pressure hole 158 is formed independently from the pressure hole 157, the back pressure hole 158 may be formed to be located in the same compression chamber V as a compression chamber V communicating with the pressure hole 157.

It may be preferable in the aspect of stabilizing behavior of the second sealing member 172 and suppressing refrigerant leakage between the compression chambers V. Furthermore, when the pressure hole 157 and the back pressure hole 158 are formed independently from each other, the pressure hole 157 and the back pressure hole 158 are not coupled to each other during processing, which may facilitate the processing of the pressure hole 157 and the back pressure hole 158.

Meanwhile, the second sealing member 172 may also be formed to have a cross-section in a U-like shape or V-like shape such that an opening of the second sealing member faces the compression chamber V or the back pressure space S3. However, as pressure of the compression chamber V is applied toward the back pressure surface portion to be described later through the pressure hole 157, the second sealing member 172 may be formed in a rectangular cross-sectional shape as shown in FIG. 4. In this case, the second sealing member 172 may be formed of a lubricating material such as Teflon.

Further, the second sealing member 172 may be formed in a complete annular ring shape with no both ends, or be formed in a cut annular shape having both ends slidably brought into contact with each other. The second sealing member 172 receives pressing force directed in an axial direction through the pressure hole 157 and simultaneously receives back pressure directed from inside to outside as it is in contact with the back pressure space S3. Therefore, the second sealing member 172 may preferably be formed in the cut annular shape for securing sealing force owing to the sliding contact between the both ends.

Meanwhile, the balance weight 136 coupled to the rotation shaft 135 is provided on one side of the second scroll 150 in an axial direction, that is, a front side of the second scroll 150. The balance weight 136 forms the back pressure space S3 together with the second scroll 150. FIG. 7 is a planar view of the balance weight according to the exemplary embodiment of the present invention.

As illustrated, the balance weight 136 according to the embodiment may be provided with an eccentric pin portion 136 a, an eccentric mass portion 136 b, and a back pressure surface portion 136 c.

A center Oe of the eccentric pin portion 136 a is disposed to be eccentric from a center Oc of the rotation shaft 135 (a center of the rotor) by an orbiting radius of the second scroll 150, and is firmly coupled to a rear end of the rotation shaft 135. The eccentric pin portion 136 a is formed in a cylindrical shape and is fixedly coupled to the rear end of the rotation shaft 135 by a fixing pin or a fixing bolt (not shown) inserted through the eccentric pin portion 136 a.

Also, the center Oe of the eccentric pin portion 136 a may preferably be formed to be concentric to a center Os of the second sealing member 172 (or a center of the back pressure protrusion portion). This is because an area of the back pressure surface portion 136 c needs to be wider than the area of the same back pressure space S3 as the second sealing member 172 performs orbiting motion with respect to the balance weight (more precisely, the back pressure surface portion 136) if the center Oe of the eccentric pin 136 a is eccentric from the center Os of the second sealing member 172 (or the center of the back pressure protrusion).

The eccentric mass portion 136 b extends in a radial direction from an outer circumferential surface of the eccentric pin portion 136 a. However, since the eccentric mass portion 136 b extends into a semicircular shape or a fan shape from one side of the outer circumferential surface of the eccentric pin portion 136 a, a center Ow of a mass is eccentric toward the eccentric pin portion 136 b with respect to the center Oe of the eccentric pin portion 136 a.

An outer diameter of the eccentric mass portion 136 b is formed so large that the eccentric mass portion 136 b is rotable in the accommodating space portion 122 of the main frame 102. For example, the outer diameter of the eccentric mass portion 136 b is formed to be smaller than an inner diameter of the accommodating space portion 122 based on an axial center Oc of the rotation shaft 135.

The back pressure surface portion 136 c radially extends to an opposite side of the eccentric mass portion 136 b from the outer circumferential surface of the eccentric pin portion 136 a. For example, the back pressure surface portion 136 c extends into a semicircular or fan shape from both side surfaces of the eccentric mass portion 136 b in a circumferential direction. Thus, an outer circumferential surface of the eccentric mass portion 136 b and an outer circumferential surface of the back pressure surface portion 136 c form a circular shape together.

Similar to the eccentric mass portion 136 b, the back pressure surface portion 136 c is generally formed to have a circular outer circumferential surface, but it is not necessarily to be circular. That is, the back pressure surface portion 136 c may be formed in any shape if the outer circumferential surface of the back pressure surface portion 136 c is always located at an outer side than an inner circumferential surface of the second sealing member 172 such that the back pressure space S3 is formed inside the second sealing member 172.

Also, an outer diameter of the back pressure surface portion 136 c may be the same as an outer diameter of the eccentric mass portion 136 b based on the center Oe of the eccentric pin portion 136 a, which is not mandatory. In fact, it is not desirable because the inner diameter of the accommodating space portion 122 should be wider in correspondence to the outer diameter of the back pressure surface portion 136 c when the outer diameter of the back pressure surface portion 136 c and the outer diameter of the eccentric mass portion 136 b are formed to be the same as each other. Accordingly, as illustrated in FIG. 7, the outer diameter of the back pressure surface portion is preferably formed to be smaller than the outer diameter of the eccentric mass portion 136 b on the basis of the center Oe of the eccentric pin portion 136 a. Therefore, a stepped portion 136 d may be formed on a point where the eccentric mass portion 136 b and the back pressure surface portion 136 c are connected to each other.

However, similar to the outer diameter of the eccentric mass portion 136 b, it may be advantageous that the outer diameter of the back pressure surface portion 136 c is formed to be larger than the outer diameter of the second sealing member 172, namely, to be substantially the same as an outer diameter of the back pressure protrusion portion 155.

In addition, the back pressure surface portion 136 c may be formed thinner than the eccentric mass portion 136 b. Accordingly, a center of gravity Ow of the balance weight 136, as aforementioned, may be positioned eccentrically toward the eccentric mass portion 136 b. However, the back pressure surface portion 136 c may alternatively be formed to be the same in thickness as the eccentric mass portion 136 c. In this case, however, the back pressure surface portion 136 c is preferably formed of a lighter material than a material of the eccentric mass portion 136 b so that the center of gravity of the balance weight 136 is eccentrically disposed toward the eccentric mass portion 136 b.

Meanwhile, the eccentric pin portion 136 a, the eccentric mass portion 136 b, and the back pressure surface portion 136 c constituting the balance weight 136 may be formed by one component or by assembling a plurality of components. However, since the back pressure surface portion 136 c forms a kind of axial bearing surface that is in sliding contact with the back pressure protrusion portion 155 or the second sealing member 172, it may be advantageous that the eccentric mass portion 136 b and the back pressure portion 136 c are formed as a single body, considering surface roughness of the bearing surface.

The motor-operated compressor according to this embodiment may provide the following operation effects.

Referring back to FIGS. 2 and 4, a refrigerant sucked into the suction space S1 through the inlet port 111 a is introduced into the suction chamber V1 by suction force generated in the compression unit 104, and is then introduced into a first compression chamber and a second compression chamber, respectively. The refrigerant sucked into each of the compression chambers V is compressed as the volume of the corresponding compression chamber is decreased while moving to a central part. Then, the compressed refrigerant flows to the discharge chamber V3 and is discharged into the discharge space S2 through the discharge port 144.

At this time, the refrigerant discharged from the compression chamber V to the discharge space S2 is separated from oil in the discharge space S2 or the oil separator 116. The refrigerant is then discharged to the refrigeration cycle apparatus through the exhaust port 113 a while the gas oil separated from the refrigerant remains in the discharge space S2 in a mist state. This gas oil is moved to the suction chamber V1 through the first oil recovery hole 113 b, the orifice 117, and the second oil recovery hole 142 a by a pressure difference, and then sucked into the compression chamber V together with the refrigerant sucked into the suction chamber V1.

Meanwhile, some of the refrigerant and oil compressed in the compression unit 104 (more specifically, some of the refrigerant and oil moved to the discharge chamber via the intermediate pressure chamber) are moved to the sealing groove 156 through the pressure hole 157. At the same time, some of the refrigerant and oil flowing to the sealing groove 156 through the pressure hole 157 moves to the back pressure space S3 through the back pressure hole 158 communicating with a side surface of the pressure hole 157.

Then, the second sealing member 172 is pushed toward a front side, that is, the back pressure surface portion 136 c of the balance weight 136 by pressure of the refrigerant and oil moving to the sealing groove 156 through the pressure hole 157. Accordingly, the second sealing member 172 is brought into close contact with the back pressure surface portion 136 c, thereby sealing the inner space of the back pressure protrusion portion 155, that is, the back pressure space S3.

The back pressure space S3 forms back pressure almost equal to discharge pressure by the refrigerant and oil moving to the back pressure space S3 through the back pressure hole 158. However, since the area of the back pressure space S3 in the radial direction is larger than the area of the discharge chamber V3 in the radial direction, back pressure required for supporting the second scroll 150 toward the first scroll 140 can be secured.

Then, the second scroll 150 is lifted toward the first scroll 140 so that an end surface of the fixed lap 143 is in contact with the first side surface 151 a of the orbiting scroll disk portion 151. When the second scroll 150 performs an orbiting motion in this state, the first pressurizing end 157 a of the pressure hole 157 is repeatedly opened and closed by the fixed wrap 143. Then, the refrigerant and oil are moved in both directions by a pressure difference between the compression chamber V (more specifically, the discharge chamber) and the back pressure space S3.

FIGS. 8A to 9B are sectional views illustrating a position of the orbiting scroll depending on a pressure difference between the compression chamber and the back pressure space in the motor-operated compressor of the present invention.

For example, as shown in FIG. 8A, when the back pressure of the back pressure space S3 is higher than the required back pressure, the second scroll 150 is lifted so that the wraps 143 and 152 and the disk portions 151 and 141 of the two scrolls 140 and 150 come into close contact with each other. This may increase friction loss between the wraps 143 and 152 of the two scrolls 140 and 150. However, as shown in FIG. 8B, when the second scroll 150 is further orbiting, the pressure hole 157 and the back pressure hole 158 are opened, so that the refrigerant and oil in the back pressure space S3 are moved to the compression chamber V (for instance, the discharge chamber). Accordingly, the back pressure of the back pressure space S3 is instantaneously lowered, adhesion between the two scrolls 140 and 150 can be decreased, thereby reducing friction loss.

On the other hand, as shown in FIG. 9A, when the back pressure of the back pressure space S3 is lower than the required back pressure, as in the case of starting the compressor, the second scroll 150 is not sufficiently lifted. As a result, the wrap 143 and 152 and the disk portion 151 and 141 of the scrolls 140 and 150 are spaced apart from each other, which may increase compression loss. However, as shown in FIG. 9B, the refrigerant and oil in the compression chamber V (for example, the discharge chamber) are moved to the back pressure space S3 and the pressure in the back pressure space S3 instantaneously rises to the required back pressure. The second scroll 150 is accordingly lifted quickly so that the wrap 143 and 152 and the disk portions 141 and 151 of the two scrolls 140 and 150 are brought into contact with each other, thereby suppressing compression leakage.

In this way, according to the present invention, since the pressure of the back pressure space interacts with the pressure of the compression chamber, the pressure of the back pressure space can vary according to the change in the pressure of the compression chamber, thereby maintaining the required back pressure. This may result in suppressing friction loss that may occur when the pressure of the back pressure space is higher than the required back pressure, and suppressing compression loss that may occur when the back pressure is lower than the required back pressure.

In addition, in the present invention, the back pressure space is formed between the second scroll and the balance weight, and the back pressure hole is formed in the second scroll so that the back pressure space communicates with the compression chamber. Accordingly, a length of the back pressure hole can be shortened and the required back pressure can be quickly formed in the back pressure space. Further, the back pressure is formed as the refrigerant and oil from the discharge chamber or the refrigerant and oil immediately before the discharge chamber are introduced into the back pressure space, which makes possible to reduce the volume of the back pressure space and to secure the required back pressure quickly. Also, the main bearing that supports the rotation shaft is installed outside the back pressure space, load applied to the main bearing can be reduced, thereby increasing lifespan of the main bearing.

Further, in the present invention, sealing force of the sealing member can be improved as the sealing member forming the back pressure space is axially supported by the pressure hole communicating with the compression chamber. Accordingly, the back pressure space can be effectively sealed even when a high-pressure refrigerant such as a CO2 refrigerant is applied, thereby securing the required back pressure.

Hereinafter, description will be given of another embodiment of a back pressure space in the motor-operated compressor according to the present invention. FIG. 10 is a sectional view illustrating another embodiment of a back pressure space in the motor-operated compressor according to the present invention.

That is, in the foregoing embodiment, the back pressure space is formed by forming the back pressure protrusion portion on the second side surface of the second scroll. In this embodiment, however, the back pressure space formed as a groove is formed in the second scroll.

For example, as shown in FIG. 10 according to an exemplary embodiment of the present invention, the back pressure space S3 may be formed by forming a back pressure space portion 159 in a recessed shape with a predetermined width and depth in the second side surface 151 b of the second scroll 150. As the boss groove 153 is formed at a central part of the back pressure space 159, the back pressure space portion 159 may be formed in an annular shape.

In this case as well, the sealing groove 156 described above is formed in an annular shape on an outer surface of the back pressure space portion 159. The pressure hole 157 described above may be formed through the sealing groove 156, and the back pressure hole 158 described above may be formed in the back pressure space portion 159 in a communicating manner. The pressure hole 157, as described in the foregoing embodiment, may be branched from the middle portion of the back pressure hole 158 or may be formed independently from the back pressure hole 158.

A motor-operated compressor employing the back pressure space according to this embodiment has a similar back configuration and provides similar operation effects to the motor-operated compressor employing the back pressure space according to the foregoing embodiment, so detailed description thereof will be omitted.

However, in case where the back pressure protrusion portion 155 of the foregoing embodiment is excluded and the back pressure space portion 159 as illustrated in this embodiment is formed in the recessed shape, the balance weight 136 is disposed closer to the compression chamber V, which makes possible to reduce the size of the eccentric mass portion of the balance weight 136. This may result in decreasing input applied to the driving motor or driving unit 103 and improving compressor efficiency accordingly.

The foregoing embodiment illustrates the motor-operated compressor to which the CO2 refrigerant is applied, however, the present invention is not limited thereto.

The foregoing embodiments are merely illustrative to practice the motor-operated compressor according to the present invention. Therefore, the present invention is not limited to the above-described embodiments, and it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the scope of the present invention. 

What is claimed is:
 1. A motor-operated compressor, comprising: a casing having a motor chamber; a frame provided adjacent one end of the motor chamber; a driving motor positioned on one side of the frame and accommodated in the motor chamber; a first scroll supported on an opposite side of the frame and having a first spiral wrap; a second scroll provided between the frame and the first scroll, the second scroll having a second spiral wrap engaged with the first spiral wrap, and forming compression chambers between the first and second wraps while performing an orbiting motion relative to the first scroll by receiving a rotational force of the driving motor; a rotation shaft having one end connected to a rotor of the driving motor and another end eccentrically coupled to the second scroll to transfer the rotational force of the driving motor to the second scroll; a balance weight coupled to the rotation shaft, one surface of the balance weight facing a rear surface of the second scroll; a sealing member provided between the rear surface of the second scroll and the one surface of the balance weight to form a back pressure space between the rear surface of the second scroll and the one surface of the balance weight; and a back pressure passage extending through the second scroll from the compression chamber to the back pressure space such that the compression chamber and the back pressure space communicate with each other.
 2. The compressor of claim 1, wherein the second scroll includes a sealing groove having a generally annular shape, the sealing member being slidably insertable in the sealing groove in an axial direction, and a pressure passage extending through the second scroll from the sealing groove to the compression chamber such that the sealing groove and the compression chamber communicate with each other.
 3. The compressor of claim 2, wherein the pressure passage has a length smaller than or equal to a thickness of the second wrap.
 4. The compressor of claim 3, wherein the first scroll includes a discharge port through which a compressed refrigerant of the compression chamber is discharged, and the pressure passage communicates with a discharge chamber, or with a compression chamber immediately before the discharge chamber.
 5. The compressor of claim 4, wherein the back pressure space has a radial area larger than or equal to a radial area of the compression chamber communicating with the pressure passage.
 6. The compressor of claim 2, wherein the back pressure passage communicates with the pressure passage.
 7. The compressor of claim 6, wherein the back pressure passage has an inner diameter smaller than or equal to an inner diameter of the pressure passage.
 8. The compressor of claim 2, wherein the back pressure passage and the pressure passage are spaced apart from each other.
 9. The compressor of claim 8, wherein the back pressure passage and the pressure passage communicate with the same compression chamber.
 10. The compressor of claim 1, wherein the second scroll includes a generally annular back pressure protrusion portion protruding toward the balance weight, a sealing groove is provided in the back pressure protrusion portion, the sealing member being slidably inserted in the sealing groove in the axial direction, and a pressure passage extends through the second scroll at a radially inner position relative to an inner circumferential surface of the back pressure protrusion portion.
 11. The compressor of claim 1, wherein the second scroll includes a back pressure space groove extending axially into the second scroll, to a predetermined depth, from a surface of the second scroll facing the balance weight, a sealing groove formed radially outward of the back pressure space groove so that the sealing member is slidably inserted into the sealing groove in the axial direction, and wherein the back pressure passage extends axially from the back pressure space groove.
 12. The compressor of claim 1, wherein the balance weight comprises: an eccentric pin portion fixed to the rotation shaft and coupled to the second scroll; an eccentric mass portion extending from the eccentric pin portion and having a center of gravity eccentrically positioned from a center of the rotation shaft; and a back pressure surface portion extending radially from the eccentric pin portion to form a back pressure space portion together with the eccentric mass portion.
 13. The compressor of claim 1, wherein the frame includes an accommodating space portion for accommodating the balance weight, and the accommodating space portion communicates with the motor chamber.
 14. The compressor of claim 13, wherein the accommodating space portion includes a generally annular and stepped bearing supporting portion, and the bearing supporting portion includes a ball bearing for supporting the rotation shaft.
 15. The compressor of claim 1, wherein the second scroll incudes a boss groove configured to receive the rotation shaft, and a bush bearing provided between an inner circumferential surface of the boss groove and an outer circumferential surface of the rotation shaft.
 16. The compressor of claim 1, wherein the casing includes a discharge space accommodating a refrigerant and oil discharged from the compression chamber, the discharge space includes an oil recollecting passage to guide a refrigerant and oil in the discharge space to a suction side of the compression chamber, and the oil recollecting passage includes a pressure reducing member.
 17. A motor-operated compressor, comprising: a casing including a driving motor; a frame fixed to the casing; a first scroll attached to the frame and having a first spiral wrap; a second scroll positioned between the frame and the first scroll, the second scroll including a second spiral wrap attached to a front surface of the second scroll, the second spiral wrap being engaged with the first spiral wrap, forming at least one compression chamber between the first and second wraps; a rotation shaft having one end connected to the driving motor and an opposite end eccentrically connected to the second scroll; a balance weight coupled to the rotation shaft, the balance weight being axially separated from a rear surface of the second scroll to form a back pressure space between the second scroll and the balance weight; and a back pressure passage extending through the second scroll, the back pressure passage fluidly coupling the at least one compression chamber and the back pressure space.
 18. The compressor of claim 17, wherein the second scroll includes: a scroll disk, the second spiral wrap protruding from one surface of the scroll disk; a generally annular sealing groove disposed on an opposite surface of the scroll disk; and a pressure passage extending from the sealing groove, through the scroll disk, to the compression chamber.
 19. The compressor of claim 18, wherein the pressure passage is radially spaced apart from the back pressure passage.
 20. The compressor of claim 18, wherein the pressure passage is positioned radially outward relative to the back pressure passage, and the back pressure passage is fluidly coupled to the pressure passage. 